1. Field of the Invention
The invention relates to a poly-V type sheet metal pulley and to the manufacture thereof, and more particularly to the manufacture of such pulleys by spinning or combined spinning and press operations and to the resultant product, wherein increased strength is imparted to the pulley product by the formation of particular cross-sectional contours in the pulley body at various stages in its manufacture as well as in the resultant pulley product.
2. Description of the Prior Art
There is a great variety of types of sheet metal poly-V pulley structures in the prior art as well as many different procedures that have been used in the manufacture thereof. The effort in the prior art has been to utilize the least amount of metal possible in the manufacture of sheet metal poly-V type pulleys, while, at the same time, satisfying strength requirements of the poly-V-grooved body portion in various zones thereof.
The pulley of U.S. Pat. No. 3,977,264, while providing adequate strength for torque loading, uses more metal than is necessary to provide the required strength at the bases of the poly-V grooves and in its radially projecting terminal flange at the open end of the pulley.
U.S. Pat. No. 4,050,321 illustrates the manner in which a stepped interior surface may be provided to reduce the thickness of the cylindrical wall portion of the cup-shaped stage blank used in forming a multiple V-grooved pulley having a groove wall sinuous in cross section.
There exists a need in the art for a sheet metal poly-V pulley having characteristics, among others, imparted by using a cup-shaped stage blank having a generally cylindrical cup wall with a stepped interior surface, in the manufacture of poly-V pulleys to provide a strong poly-V-grooved body and one with less metal than characterizes prior art sheet metal poly-V pulleys. Further, there is a need for a poly-V pulley having particular cross-sectional contours for the angular outwardly projecting single wall flange which defines the open end of the V-grooved body.